c# - 如何获取组的最新值

Question

我从下面给出的查询中得到 15 行，得到的值也显示在下图中

SELECT * FROM [SS_MatrixLearners] 
WHERE ssml_Id_learnercourse=7390 and ssml_id_matrix = 29 and ssml_Id_topic=47 
order by SSML_Id_LevelKey, SSML_Id_LevelValue

对于所有这些值，我还想要一个在列SSML_CompletedByUserName中具有最新日期的值。SSML_CompletionDate请帮助我如何获得该价值。仅供参考，我正在使用 c# 在 Web 表单中使用它

Answer 1

我想出了以下解决方案。

SELECT * into #temp FROM (SELECT * FROM [SS_MatrixLearners] ORDER BY SSML_ID_LevelKey, SSML_Id_LevelValue) As rn FROM [SS_MatrixLearners] where ssml_Id_learnercourse = 7390 and ssml_id_matrix = 29 and ssml_Id_topic = 47) t WHERE rn = 1 Update #temp SET SSML_CompletedByUserName = ( select top 1 ISNULL(SSML_CompletedByUserName,'') From [SS_MatrixLearners] WHERE ssml_Id_learnercourse=7390 and ssml_id_matrix = 29 and ssml_Id_topic=47 ORDER by SSML_CompletionDate desc ) SELECT * from #temp order by SSML_Id_LevelKey, SSML_Id_LevelValue DROP table #temp

如果能写一些优化查询就好了。